1. Field of the Invention
The present invention pertains to pipe machining apparatus. More specifically, the present invention pertains to apparatus for cutting and/or beveling the ends of pipe sections in preparation for welding the pipe sections together in the construction of a pipeline.
2. Description of the Prior Art
In the construction of cross-country or underwater pipelines, sections of large diameter steel pipe are laid end-to-end, aligned and joined by welding in the field. The ends of the pipe are sometimes preshaped with beveled ends to provide end formations or bevels suitable for welding. In some cases, such machining is accomplished in a large stationary pipe mill. In the field, the sections of pipe are laid end-to-end, aligned and welded together.
In the past, welding of pipe joints was accomplished totally by skilled welders. More recently, automatic and semi-automatic welding equipment has become much more common. Automatic and semi-automatic welding of large diameter pipe requires that the ends of the pipe be more precisely cut. Thus, there has been an increased demand for precision machinery suitable for finishing pipe ends in the field, preparatory to welding. Such machines need to be able to grip the pipe firmly and to cut or bevel the end of the pipe in a plane which is perpendicular to the axis of the pipe. Variations in pipe wall thickness and minor deviations from true round cross-section make it desirable to design the field cutting machine so that it follows the actual contour or surface of the pipe, preferably using the interior surface as a reference.
Several pipe cutting and/or beveling machines have been developed which are suitable for in-the-field machining, preparatory to aligning and welding sections of pipe in pipeline construction. Examples of such are shown in U.S. Pat. Nos. 3,608,406; 3,733,939 and 4,126,065. Such prior art machines are typically provided with a clamping section which supports the working equipment in or on the pipe and a cutting section which usually provides a large circular plate or cutting head which rotates adjacent and parallel to the end of the pipe being cut. Plural arms, mounted on the plate, carry cutting tools and some type of power device rotates the plate as the cutting tools cut the end of the pipe. The plate is also adapted for coaxial movement with the pipe, moving the cutting tools into and away from cutting engagement with the end of the pipe. Although these prior art machines provide a number of advantages over the old cutting and welding techniques of the past, improvements are still desired.
The pipe used to form pipelines vary greatly in diameter. Although they may be smaller or larger, the vast majority of pipelines have diameters ranging from 16" to 48" in diameter. The pipe machines of the prior art are not easily adaptable for use with such a wide diameter range. The clamping and cutting sections of such machines may be suitable for a specific diameter pipe but may require substantial changes for a smaller or larger diameter pipe. For this reason, the prior art requires several machines to cover a range of 16" to 48" diameter pipe. Some of the pipe cutting machines of the prior art may be constructed in such a way as to allow the clamping section and the cutting section to be disconnected and another clamping section attached to the cutting section to accommodate a different size pipe. Since the clamping section is typically actuated by hydraulic powered devices, hydraulic lines and other connecting members must be disconnected and reconnected when the clamping sections are changed. Not only does this require considerable time and manpower it may result in loss of hydraulic fluids and creation of hazardous conditions around the working area thereof.
In addition, the cutting elements of the cutting sections of pipe machines of the prior art do not always provide smooth finishes. Some are subject to chatter and vibration while others do not provide smooth advancement of the cutting tools against the end of the pipe. A number of problems have been encountered with these cutting sections, particularly those for larger diameter pipe.